1. Field of the Invention
This invention relates generally to bearings for carrying rotating shafts and more particularly to a combination journal and thrust bearing assembly.
2. Related History
The support of rotating shafts subject to axial loads has presented significant problems. While sleeve bearings have provided a relatively low cost, efficient and easily serviceable approach for supporting shafts which were relatively free of axial stress or loads, journal bearings alone were incapable of restraining a rotating shaft against axial movement.
Combination journal and thrust bearing assemblies heretofore were generally custom designed for each application and were formed of one piece including a sleeve for accommodating radial load forces with a unitary transverse flange for axial loads. A typical example is illustrated in the article appearing in Konstruktion 41, (1989) by Schmon, et al. entitled: Auslegung Und Betrieb yon Radial-Axialbund-Gleitlager pp. 89-94, FIG. 1 at p. 90. A further example of a combined journal and thrust bearing is illustrated in Soviet Union patent 1,370,336. By utilizing the same bearing material in a one piece bearing for both the radial load portion and the axial load portion of the bearing, inherent disadvantages resulted. For example, should one of the two bearing load components wear before the other, the entire bearing was required to be replaced.
The normal load carrying capacity of a bearing, expressed as a PV factor (pressure times surface velocity) of a journal bearing was generally four to five times greater than the PV factor for the same bearing material employed as a thrust bearing. If the same material was utilized for both bearing applications in a one piece bearing, the bearing was often overdesigned for one of its two functions.
The inventor perceived a need for a combined journal and thrust bearing wherein bearing materials suitable for the anticipated radial and axial loads are separately selected and wherein the journal bearing components may be replaced independently of the thrust bearing components and the thrust bearing components may be replaced independently of the journal bearing components.